# EE6504 Electrical Machines II Nov Dec 2016 Important Questions

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B.E/B.TECH DEGREE EXAMINATION NOV / DEC 2016
Fifth Semester
Department of EEE
EE6504 Electrical Machines II
Nov Dec 2016 Important Questions
(Regulation 2013)

16 Marks Important Questions asked in previous years university examinations.

1. Explain with neat sketch the principle of working of single phase induction motor with neat sketch by double field revolving theory and also draw torque slip characteristics.
2. Explain split phase induction motor and capacitor start induction motor and also draw the slip torque characteristics.
3. Explain the principle of operation and applications of repulsion motor and hysteresis motor.
4. Explain why single phase induction motor is not self-starting and draw its equivalent circuit.
6. Explain with neat sketch the static Scherbius system and Kramer system of three phase induction motor.
7. Describe the following methods of speed control of slip ring induction motors: i)Using external rotor resistance ii) Slip power recovery scheme
8. With neat diagrams , explain the working of any two types of starters used for starting 3 phase squirrel cage induction motors.
9. Explain with neat sketches the different methods of speed control.
10. Explain Cascade connection in detail.
11. A 10 KW (output), 3300V,3 phase star connected induction motor has synchronous speed of 500 rpm. The full load slip is 1.8%.and full load power factor is 0.85.Stator cu loss=2440W.Iron loss=3500 W. rotational losses= 1200W. stator losses =700 W. Calculate i) rotor cu loss ii) line current ii) full load efficiency.
12. Explain the method of finding regulation for the following methods. i) ASA method ii) Potier method
13.  Describe the principle and construction of slow speed operation generator with neat diagram and derive the emf equation of alternator.
14. Develop an equivalent circuit for three phase induction motor. State the difference between exact and approximate equivalent circuit.
15. Derive the equation for torque developed by an induction motor .Draw a typical Torque – slip curve and deduce the condition for maximum torque.
16. Using relevant phasor diagrams, describe the effect of changing the excitation on the armature current and power factor of a synchronous motor and thereby obtain ‘V’ and inverted ‘V’ curves.
17. Explain how rotating field is produced in two phase and three phase induction motor
18. Derive the expression for power developed in a 3 phase synchronous motor in terms of E, V, Zs, and θ
19. A 75 kW,400V, 4 pole, 3 phase, star connected synchronous motor has a resistance and synchronous reactance per phase of 0.04ohm and 0.4ohm respectively. Compute for full load 0.8pf lead the open circuit emf per phase and gross mechanical power developed. Assume an efficiency of 92.5%.
20. Define armature reaction and explain the effect of armature reaction on different power factor loads of synchronous generators.